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Introduction to the type of rechargeable battery

Oct. 30, 2019

  As a Ni-MH Battery Pack Supplier, there is some information to share with you. Rechargeable batteries mainly include lead-acid batteries and alkaline batteries. Currently used nickel-cadmium (NiCd), nickel-hydrogen (NiMH) and lithium-ion (Li-Ion) batteries are alkaline batteries.

Ni-MH Battery

Ni-MH Battery

  The Ni-MH Battery battery positive plate material is NiOOH, and the negative electrode plate material is hydrogen absorbing alloy. The electrolyte is usually a 30% aqueous KOH solution with a small amount of NiOH added. The separator is made of a porous vinylon nonwoven fabric or a nylon nonwoven fabric. Ni-MH batteries are available in both cylindrical and square sizes.

  The Ni-MH battery has good low-temperature discharge characteristics, and even when it is discharged at a high temperature (at a discharge rate of 1 C) at an ambient temperature of -20 ° C, the discharged electricity can reach more than 85% of the nominal capacity. However, when the Ni-MH battery is at a high temperature (+40 ° C or higher), the storage capacity is reduced by 5 to 10%. This capacity loss due to self-discharge (the higher the temperature, the higher the self-discharge rate) is reversible, and several charge and discharge cycles can be restored to the maximum capacity. The Ni-MH battery has an open circuit voltage of 1.2 V, which is the same as the NiCd battery.

  The charging process of Ni-Cd/Ni-MH batteries is very similar and requires constant current charging. The difference between the two is mainly in the fast charging termination detection method to prevent the battery from being overcharged. The charger performs constant current charging on the battery while detecting the voltage and other parameters of the battery. When the battery voltage rises slowly to a peak, the rapid charging of the Ni-MH battery is terminated, and the Ni-Cd battery terminates the fast charging when the battery voltage drops by -ΔV for the first time. In order to avoid damage to the battery, the battery cannot be started to charge quickly when the battery temperature is too low. When the battery temperature Tmin is lower than 10 °C, it should be switched to the trickle charging mode. Once the battery temperature reaches the specified value, it must stop charging immediately.

  The active material on the positive electrode of Ni-Cd Battery is composed of nickel oxide powder and graphite powder. Graphite does not participate in chemical reaction, and its main function is to enhance conductivity. The active material on the negative electrode plate is composed of cadmium oxide powder and iron oxide powder. The function of the iron oxide powder is to make the cadmium oxide powder have high diffusibility, prevent agglomeration, and increase the capacity of the electrode plate. The active materials are respectively wrapped in the perforated steel strip, and become the positive and negative plates of the battery after press molding. The plates are separated by an alkali-resistant hard rubber insulating rod or a perforated polyvinyl chloride corrugated board. The electrolyte is usually a potassium hydroxide solution. The self-discharge rate of the Ni-Cd battery (i.e., the rate at which the battery loses its charge when not in use) is moderate compared to other batteries. When the Ni-Cd battery is in use, if the discharge is not complete, it will be charged again. When it is discharged again, it will not be able to discharge all the power. For example, after releasing 80% of the power and then fully charging, the battery can only emit 80% of the power. This is the so-called memory effect. Of course, several complete discharge/charge cycles will return the Ni-Cd battery to normal operation. Due to the memory effect of the Ni-Cd battery, if it is not completely discharged, each battery should be discharged below 1V before charging.

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